In the winding process of present-day spinning mills, wide use is made of auto-winders with automatic thread-knotting machines. Among these auto-winders with automatic thread knotting machines, auto-winders with movable automatic thread-knotting machines, such as the auto-winder made by Schlafhorst GmbH of West Germany, have taken the lead among auto-winders with automatic thread-knotting machines because of their superiority in the quality of the wound thread package, their reliability of operation, and their economy.
In an automatic thread-knotting machine, a broken thread is mechanically knotted and the knotted thread is immediately wound. Therefore, in comparison with an ordinary knotting method in which the thread is wound after the configuration of the thread knot is confirmed, there is a larger probability of inferior knotting in a thread knot in an auto-winder, e.g., doubling of two threads in knotting (below, "two-plied thread"), intermixing of waste thread in knotting, and irregular lengths of ends of knotted thread. The winding process is the last process in the thread-producing process, therefore, the above-mentioned inferior knotted portion is not removed in subsequent processes but is maintained as is in the thread package and supplied to the knitting process or weaving process. In present knitting processes or the weaving processes, 80% of all defects are caused by inferior thread-knotting portions in the above-mentioned winding process. Use of thread from which the inferior knotting portion is not removed decreases the product yield due to the increased rate of inferior fabric. Further, use of the inferior fabric for the finished goods decreases the quality of the finished goods.
To prevent occurrence of inferior thread knotting in the winding process during the winding process itself, automatic thread-knotting machines of recent auto-winders have been provided with thread-knotting monitors. A thread-knotting monitor is comprised of an optical device having a light-emitting element and a light-detecting element or an electrostatic-capacity measuring device for measuring the fluctuation of electrostatic capacity; a comparator for comparing the signal emitted from the measuring device with a predetermined value; and a device for cutting the thread which began to run after receipt of a signal from the comparator. The monitor is arranged adjacent to a thread-knotting mechanism of the automatic thread-knotting machine. That is, the measuring device of the thread-knotting monitor is arranged downstream of the thread-knotting mechanism in the direction of thread advance and detects the thickness of the running thread. When inferior knotting occurs and the thread continues to run as it is, the thickened thread-knotting portion is measured by the measuring device, and the comparator, in which a predetermined value, i.e., a monitoring standard, is set, compares the thickness of the thread-knotting portion with the monitoring standard. When the thickness of the thread-knotting portion is larger than the monitoring standard, the comparator emits a signal to the thread-cutting device. Thus, use of this known thread-knotting monitor enables a large reduction of inferior thread-knotting portions in a thread package. Now, a controller for adjusting the monitoring standard to set the monitoring standard to correspond to the thickness of the thread used is provided with the thread-knotting monitor.
While the above known thread-knotting monitor performs excellently to detect and remove inferior thread-knotting portions, it conversely has the following disadvantages. That is, in the measuring device used in the thread-knotting monitor, the monitoring standard tends to fluctuate with the passage of time. Further, even if the measuring device fails in operation, no means is provided for detecting this failure. Therefore, there is a possibility of thread knotting continuing without operation of the measuring device, resulting in overlooking of the occurrence of inferior thread knotting. Further, even if the thread-knotting monitor is normal, inferior thread knotting sometimes occurs due to defects in the thread-knotting mechanisms, e.g., failure of operation of a cutter. Conventional thread-knotting monitors have a disadvantage in that they operate without relation to the performance of the thread-knotting mechanism.
Therefore, when a thread-knotting monitor is used for a long time, inferior thread knotting is sometimes not removed or excess cutting occurs, i.e., inferior thread-knotting portions not requiring removal or normal thread-knotting portions are sometimes cut. Therefore it is necessary to inspect and adjust the thread-knotting monitor at constant time intervals. At present, in the case of 24-hour operation, auto-winders having the above thread-knotting monitors are inspected two to three times a day so as to eliminate the problem. Specifically, in such inspection work, the above-mentioned two-plied thread is passed through the thread-knotting monitor as an adjustment sample, and adjustments are made so that threads with inferior thread-knotting portions are reliably cut. At the same time, the measuring device and thread-knotting mechanism are inspected and defective portions are adjusted.
This inspection work requires a considerable time. A spinning mill having 30 Schlafhorst auto-winders, a representative auto-winder with a movable automatic thread-knotting machine, will have, for example, up to 150 thread-knotting monitors requiring at least 3.5 hours for inspection work. Since this inspection work must be performed at least two times per day, full-time inspection workers must be deployed, thus having a significant impact on personnel costs in the spinning factory. Further, in the case of inspection by workers, breakdowns on the measuring device occurring in the interval between inspections, e.g. 12 hours in the case of two inspections per day, are left undetected until that next inspection, resulting in inferior thread-knotting portions produced within the above time interval being passed on as is.